The present invention concerns a hydrodynamic brake, of the Foettinger type, including a bladed rotor wheel and a bladed stator wheel which together form a toroidal working chamber that is variably filled with working fluid for selectively applying and releasing braking force between two objects connected by the hydrodynamic brake.
Such a hydrodynamic brake is known from German Application, DE-OS No. 17 50 272. In that case the blades of the rotor and/or stator blade wheel are swingable about respective radially oriented axes in order to control the braking torque and in particular to reduce the air resistance loss in the brake during the disconnected condition of the brake (i.e. reducing the power consumption in the empty condition of the working chamber of the brake). In the engaged or operative condition of the brake, the swingable blades have swivelled to their ordinary oblique orientations with respect to the direction of rotation of the rotor blade wheel, which assures a high braking torque. With reference to the direction of rotation of the rotor, this is the so-called skewed position. In this case, the rear blade edges lie against the wall of the torus. In the disengaged condition of the brake, on the other hand, i.e. with the working chamber empty, the blades swivel to extend parallel to the direction of rotation and thus provide virtually no air resistance to the rotation of the rotor blade wheel.
It is believed that this known brake has not been introduced into actual practice, probably because different braking torques can be simply selected by changing the degree of admission of working fluid into the brake and that other well-proven measures have also been found for reducing the air resistance loss in the working chamber, for instance as shown in German Pat. Nos. 16 75 263, 21 35 268, and 22 27 624.
However, when a hydrodynamic brake which acts independently of the direction of rotation of the rotor blade wheel has been required, two operating spaces have had to be provided, for instance in accordance with German Pat. Nos. 16 00 191 or 27 57 240. This is unsatisfactory.